A question about zinc oxide everyone really wants to know about.  Is zinc oxide ingredient found in natural sunscreens really safe?  The New Health Cycle has done extensive research to give you the answer.

The truth is, it is safe unless zinc oxide sunscreen is used in certain scenarios.

What are the scenarios that can make zinc oxide unsafe?

  • Swimming in pools treated with chemicals
  • When exposed to UVB rays
  • Using on young children who can accidentally ingest it while eating foods high in vitamin C at the same time
  • Using nanoparticles vs microsized
  • Swimming in natural water sources with plant and marine life

It may seem these scenarios describe everything about summertime…

Before I get into the details about how zinc oxide can become unsafe when used in these scenarios, let’s talk about how unsafe it can be.

What types of possible unsafe reactions can occur from using zinc oxide in sunscreens?

  • Skin Irritation
  • Irritation in the GI and respiratory tract
  • Eye irritation
  • Nausea
  • Cytotoxicity and genotoxicity
  • Not as efficient in blocking UVB rays as it is UVA rays still posing a degree of skin cancer risk from the sun.
  • Possible carcinogenic effects have not been established due to lack of data.

The main goal of sunscreen is to prevent skin cancer caused by the sun.  Zinc oxide can do that with some limitations.  I’m sure you’re really wondering if there are any unsafe effects that can happen when using zinc oxide and there clearly are and some are not clearly known due to limited research.

These reactions do not always occur but can occur and we will discuss how with each scenario.

How can zinc oxide be unsafe while swimming in a pool?

To find out how zinc oxide can become unsafe when applying it as sunscreen before entering a swimming pool, we need to understand that zinc oxide is a chemical.  What do chemicals do?  They can spontaneously react with other chemicals.

What chemicals in a pool can zinc oxide react with?  Hydrochloric acid is the most commonly used chemical to treat the pH of pools and to kill viruses and bacteria by entering their cell wall and oxidizing the interior of the bacterium or “burns up”.

Preventing bacterial infections are a good thing so chemicals do have their benefits but what happens when you mix zinc oxide and hydrochloric acid?

Zinc oxide and hydrochloric acid can react with each other and produce zinc chloride.  Zinc chloride is a corrosive chemical and has its own hazardous substance fact sheet.

Now zinc chloride will be diluted with the water making the harmful effects very minimal, especially if only one person in the pool is wearing zinc oxide sunscreen.

Let’s think about another pool scenario that could make zinc chloride more harmful and that would be when there are many people in the pool wearing zinc oxide sunscreens and also urinating introducing more chemicals like nitrogen and people wearing other chemicals from different kinds of makeup and sunscreens out there.  You get the point now of the chemical soup that you are now swimming in.

Now also imagine swimming in this chemical soup at least once a week during the summer or some of you may swim in pools more than that.  The more time spent in a chemical soup, the more accumulation can happen.

When zinc chloride is in its gaseous form, it is much more harmful but in a pool, the likely form of exposure is in the eyes and through ingestion of the pool water.  I think we can safely say most young children gulp a hefty amount of pool water when swimming.

Ingestion of too much zinc chloride can cause intoxication, irritation of the stomach, nausea vomiting and diarrhea according to this chemical data sheet.  How much zinc chloride can cause these effects are unknown but it is also unknown how much is being introduced into the water.  There are quite a bit of unknowns here but the possibility of harm is there.

Another problem to think about when the chemicals are interacting is how much hydrochloric acid is left to do its job in killing viruses and bacteria in the pool when zinc oxide is introduced?  Hydrochloric acid is constantly being broken down into hydrogen, chlorine, and oxygen and combining again to the acid form while in the water.  This is a typical mechanism of chemicals to maintain balance.

When zinc oxide is being broken down into zinc and oxygen, the zinc will occupy some of the chloride inhibiting the formation of some hydrochloric acid reducing the efficacy of the acid to kill viruses and bacteria.  This is a secondary hazard that can occur in a swimming pool.

But zinc oxide is stable in water, how can it dissociate and be able to react with hydrochloric acid at all?   We need to get into more science involving how UVB rays from the sun react with zinc oxide.

What happens to zinc oxide when exposed to UVB rays to make it unsafe?

According to this UV interaction study with zinc oxide, UVB ray interaction with zinc oxide causes it to dissociate into free zinc and reactive oxygen.  This dissociation could be the reason why zinc oxide is less effective at protecting against UVB rays than UVA rays AND how the free zinc ions can now react with the free chloride ions in pool water.

These chemical reactions cause chain reactions leading to more unpredictable hazards.

The extent of this reaction can’t be measured with exactly how much zinc oxide is reacting with UVB rays but it can happen to expose parts of our bodies to UVB rays.  UVB rays damage skin DNA cells directly and are known to cause most skin cancers.

Zinc oxide still remains an effective chemical to reflect UVA rays that are more prevalent than UVB.  However, UVB rays are highest during the summer and hottest times of the day.

To further explore possible harmful interactions with zinc oxide during the hot summer months, let’s dive into some possible food interactions that could make using a zinc oxide sunscreen harmful.

How can zinc oxide be unsafe for young children who eat foods high in vitamin C?

I found this interesting article describing harmful effects when small amounts of zinc oxide are consumed along with foods high in vitamin C.  In this scenario, it mainly concerns those young children who may have used their hands to rub in their sunscreen and possibly still have some globs of it on their fingers.  They then typically stick their fingers in their nose or their mouths soon after.

Consuming the zinc oxide by itself is not exactly harmful compared to eating say a watermelon, orange or drinking juice at the same time.  The harmful effects are greater when combined with vitamin C.

The study showed a small amount of zinc oxide nanoparticle combined with vitamin C exhibited significant cytotoxicity.  The study only used zinc oxide nanoparticles leaving similar hazards unknown for microparticles.  This leads us to discuss the difference between nanoparticle zinc oxide vs. microparticle.

Nanoparticle zinc oxide vs microparticle

Nanoparticles are becoming increasingly popular especially in sunscreens causing the lotion to become more clear or invisible rather than leave a white pasty look on your skin.  This is the only benefit compared to microparticle which is the larger compound.  The nanosize and microsize have the same efficacy to its sunscreen job, but the nanoparticles come with hidden hazards.

Zinc oxide nanoparticles can induce disorganization of the cellular membrane due to their accumulation – ScienceDirect

The accumulation that this quote is talking about is in our skin’s hair follicles.  Cytotoxicity AND genotoxicity have been observed especially with long-term nanoparticle zinc oxide are used.

Most zinc oxide natural sunscreens are now made with nanoparticles unless it says non-nano.  Those products will likely tell you the harmful effects of using nanoparticles as well.

The microparticle size seems to be safer than the nanoparticle but caution should be taken from the previous scenarios described.

Can zinc oxide be unsafe for plants and marine life?

We have talked about the possible harmful effects for people in the previous scenarios but if you have been following The New Health Cycle’s blogs, you may have figured out that introducing chemicals to the environment can also cycle right back into our food chain and harm us again.

Zinc is an essential trace micronutrient all life needs in their diet.  Children under 8 need about 3-5 mg of zinc and adults need around 8-13 mg of zinc per day.

Marine life and plants also require a trace amount but just like most trace elements we need, too much is toxic.  The same rule applies to plant and marine life.

This article highlights how too much zinc entering our environment will eventually end up in our food increasing our intake of zinc to possibly dangerous levels.

Fish can collect zinc in their bodies from the water they swim in and from the food they eat. – Agency for Toxic Substances and Disease Registry

It’s unlikely to see the health effects of too much zinc in our diet immediately but plants and marine life are more sensitive to unbalances in their environment.

The main hazard in the environment comes from the mining of zinc to make the sunscreens and disposal.  These processes release concentrated levels that eventually end up in the water systems.

Why is Zinc oxide recognized safe by the FDA?

You can find the approved FDA report here that marks zinc oxide as a substance generally recognized as safe.  Looking at the report, it is very short and doesn’t distinguish between nanoparticles or microparticles.

The FDA fails to understand the concept of accumulation over time just as I have seen them fail when setting limits of carcinogens in our water such as arsenic.

I have also seen where the FDA fails at giving us all the information needed to feel safe such as not requiring all the nutrition facts on our food labels.

My assessment of the verbiage “generally recognized as safe” would be generally safe when not practicing typical summertime activities and not using over long periods of time.

If our trust in FDA recommendations are failing, what could be a safer natural alternative for sunscreen?

What is a safer natural alternative to zinc oxide sunscreen?

I recommend using a natural oil such as olive oil as the base of your natural sunscreen to use that is possibly a safer alternative if used correctly.   I say possibly as it would need to be reapplied more frequently than commercial sunscreens that contain chemicals to help stay on your skin when in water.

Olive oil is completely safe and won’t oxidize unless you plan on being out in 200 degrees Celsius heat. In that case, it will give off toxic fumes, but you’re most likely not surviving anyhow at those temperatures.

It is also safe for the environment.  Olive oil is non-toxic to marine life.

I discuss in full detail my recommendation for a DIY natural oil sunscreen in this article that will give you the scientific facts on how effective and safe it is.

Here are the scientific facts. It’s up to you to weigh out the benefits and the possible harmful effects.


Zinc oxide natural sunscreen ingredient is considered “generally” safe by the FDA but the FDA fails to inform the public on HOW it has been deemed safe.

From our research of reliable studies, zinc oxide nanoparticles are more harmful than microparticles by accumulating in skin hair follicles and it’s oxidative nature.

It can become unsafe when introduced to chemicals such as hydrochloric acid in swimming pools and if accidentally ingested with foods containing vitamin C.

UVB rays from the sun can oxidize zinc oxide into free radicals losing its effectiveness to block the skin from skin cancer risk associated with UVB rays.

Free zinc radicals are harmful to plant and marine life when accumulation happens.  Accumulation can happen from mining for zinc oxide, waste products, and many people swimming in a water source wearing sunscreen containing zinc oxide.

Natural olive oil based sunscreen mixtures are safer if applied correctly for people and the environment.

We hope this article was helpful to you in your journey for the safest natural sunscreen options.  Be sure to follow our Facebook page if you would like to see our blogs show up in your news feed!